Process of forming a uniform batt from staple fibers

ABSTRACT

A procedure for processing staple fibers into uniform batts by the use of a water spray to wet the fibers and a compression device to depress the fibers more densely into batt form.

United States Patent [191 Bonner et al.

[ PROCESS OF FORMING A UNIFORM BATT FROM STAPLE FIBERS [75] Inventors: Willard H. Bonner, Robert L. Craven, both of Wilmington, Del.

[73] Assignee: E. I. duPont de Nemours and Company, Wilmington, Del.

[22] Filed: Nov. 15, 1971 [21] Appl. N0.: 198,815

Related US. Application Data [63] Continuation-impart of Ser. No. 8,600, Feb. 4, 1970,

abandoned.

[52] US. Cl. ..l9/66 R, 19/105 [51] Int. Cl. ..D0lb 3/04 [58] Field of Search ..l9/66 R, 105

[ 51 Feb. 27, 1973 [56] References Cited UNITED STATES PATENTS 1,642,092 9/1927 Smith ..19/66 R FOREIGN PATENTS OR APPLICATIONS 840,508 7/1960 Great Britain 19/105 Primary ExaminerDorsey Newton Attorney-Gary A. Samuels [57] ABSTRACT A procedure for processing staple fibers into uniform batts by the use of a water spray to wet the fibers and a compression device to depress the fibers more densely into batt form.

1 Claim, 2 Drawing, Figures PATENTED R 2 1915 7 3,717. 904

INVENTOR5 WILLARD H. BONNER ROBERT L. CRAVEN ATTORNEY PROCESS OF FORMING A UNIFORM BA'I'I FROM STAPLE FIBERS CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 8,600, filed Feb. 4, 1970, now abandoned.

BACKGROUND OFTI-IE INVENTION 1 Field of the Invention This invention concerns an improved process for processing staple fibers into fibrous batts. The process is especiallysuited for use with gasinflated, closedcell-foa'm, staple fibers (hereinafter referred to as pneumacel fibers).

2. Description of the Prior Art Pneumacel fibers are very low density cellular fibers which have excellent pneumatic properties. In general, these fibers are made from synthetic organic polymers and are composed predominately of small, polyhedralshaped, closed cells, the cells being defined by thin, film-like walls of polymer. Gas entrapped within the cells contributes to the stiffness and pneumatic behavior of the cellular fibers. These fibers, in batt form, are useful as cushioning layers in mattresses, sleeping bags, or upholstered furniture, or for thermal insulationin garment linings and comforters, or for carpet cushion underlays.

Staple fiber feeding and processing machines, commercially known as hopper-feeders, conveyors, or openers, pin elevators, cards and gametters are widely used to process conventional textile fibers into batt form. A typical prior-art machine is describedin US. Pat. No. 3,158,291. This pin elevator machine in cludes a hopper portion through which staple fibers pass orin which they are stored temporarily. At the bottom of the hopper is an endless conveyor which forwards fibers from the hopper into engagement with an upwardly moving endless spiked lattice.'The spiked lattice picks up fibers from the conveyor and moves them upwardly out of the hopper portion. Adjacentthe top of the spiked lattice is a Sargent comb which oscillates in close proximity to the spiked lattice to strip excess fibers therefrom so that upwardly beyond the comb the lattice carries a fiber web or mat of generally uniform thickness. Arotating, spiked stripper roll, or hopperbeater roll can be used in place of the Sargent comb. A short distance below the point where the spiked lattice carrying the fiber web starts its downward path there is usually located a rotating doffer roll, which strips the fibers from the lattice and allows them to fall downwardly, in an opened condition, through a discharge opening in the machine. The fibers fall to an endless conveyor to form a continuous loose batt or they enter other types of processing equipment.

Several difficulties are encountered in using conventional staplefiber feeding and processing machines to prepare batts from pneumacel fibers. These apparently arise from l the very high surface-to-mass ratio of the pneumacel fibers, (2) their high surface friction, (3) their tendency to develop high electrostatic charge, (4) the stiffness or turgidity of the pneumacel fibers and (5) their low tensile strength (0.8 vs. 2-4 grams/denier for conventional fibers). It was found that when pneumacel fibers are consolidated into a batt, as results when a conventional staple fiber feeding and processing machine is used, and the batt is fed to a card, gamett or other machine for further fiber separation, the energy required to separate the fibers was greater than the fiber strength,resulting in massive breakage of the fibers into short, useless lengths of about one-sixteenth to one-eighth inch. Pneumacel fibers also have a tendency to form clumps or balls.

Thus, when these fibers are conveyed to the spiked lattice, they tend to be picked up in clumps which are stuck on the tips of the spikes. Subsequently, on reaching the stripper roll of Sargent comb, the clumps are stripped from the spikes, leaving the lattice sparsely and nonuniforrnly loaded. In addition, the high electrostatic charges developed on the pneumacel fibers cause the fibers to be attracted to various parts of the machinery and to further accumulate into balls and clumps, which in turn, when they fall off, can lead to jamming of the equipment and in further nonuniformities in the collected batt. The nonuniformities are evident as thin and heavy spots, or even holes, in the batt.

SUMMARY OF THE INVENTION The present invention is an improvement over conventional batt-forming processes and is especially adapted to the continuous opening, conveying and depositing of pneumacel fibers into a continuous,

uniform, nonwoven batt.

Thus, the invention is defined as follows: In the wetting the fibers prior to their engagement with the upwardly moving lattice until the wetted fibers contain between about 0.3 to about 3.0 pounds of water per pound of fiber, and

compressing the fibers into a mat as they are moved by the spiked lattice.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 schematically represent conventional staple fiber feeding and processing machines. FIG. 2 differs from FIG. 1 only in the location of a doffer roll and a discharge opening.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a staple fiber feeding and processing machine. The machine has rigid enclosure 10, which is suitably supported by means not shown. Enclosure 10 has an inlet opening 11, through which fibers 12 are fed. Supported (by means not shown) at the bottom of the enclosure 10 below i the inlet opening 11 is an endless conveyor having an apron 118 trained over front and rear rollers 20 and 22. In operation, the conveyor collects and moves the fibers forwardly to a dischargepoint and into engagement with an upwardly moving and forwardly extending spiked lattice 24 trained over upper and lower rollers 26 and 28. The lattice spikes 25 typically project upward at a 45 angle from the lattice surface. The spiked lattice 24 picks up fibers and moves them upwardly. Adjacent the top of spiked lattice 24 is a spiked stripper roll 30 which rotates counterclockwise (i.e., in a direction opposite to the upwardly moving lattice 24). The tips of spikes 31 of the stripper roll 30 almost touch the tips of spikes 25 of the lattice 24. Stripper roll 30 removes surplus fibers 6 from the spiked lattice 24 and directs them back toward the conveyor 18. Lattice 24 carries the remaining fibers upwardly of roll 30 in the form of a web or mat of generally uniform thickness. In front of upper roller 26 on the downwardly moving side of spiked lattice 24 is a doffer roll 32 having spikes 33. Doffer roll 32, which rotates clockwise (i.e., in the same direction as the downwardly moving lattice 24), strips the fibers from lattice 24 and directs them downwardly, in an opened condition, through a discharge opening 35 in an overhanging portion of enclosure 10. The fibers are then collected as a loose batt on a conveyor (shown partially in the figure) having an endless apron 36 trained around rollers 38. The conveyors, stripper roll, and doffer roll are driven by conventional drive means (not shown) the directions indicated by the arrows.

Water spraying means 1 are provided, preferably above the conveyor 18. The spraying means include appropriate reservoirs, valves, piping and atomizing or spraying nozzles.

A compaction means is located about midway between stripper roll 30 and the bottom of spiked lattice 24 adjacent to the upward moving portion of the lattice. The compaction means shown in FIGS. 1 and 2 is a smooth-surfaced compaction roll 3, which may be of steel, extending across the entire width of spiked lattice 24. The roll 3 clears the tips of spikes 25 (i.e., about one-half inch. In operation, compaction roll 3, which is supported and driven by conventional means not shown in the figures, rotates clockwise, i.e., in the same direction as the upwardly moving portion of spiked lattice 24) at a peripheral velocity equal to about one half that of the upwardly moving lattice 24. Wetted fibers, or clumps or wetted fibers 2, that are stuck on the ends of the lattice spikes 25 are forced by compaction roll 3 into the spaces 4 between the spikes 25. The excess pneumacel fibers, which spring back above the tops of the spikes, are subsequently removed by stripper roll 30 and directed downward toward the conveyor 18. Thus, when the compaction means is used the spiked lattice is more unifonnly and more heavily loaded than is possible with the prior art devices.

Preferably the spikes 25 are about 1.5 inches long andextend at about 45 about one inch'above the surface of lattice 2A. These spikes are about one-half inch longer than the conventional spikes of the prior art.

The heavier and more uniform loading of the spikedv lattice in the apparatus results in higher throughputs at the same lattice speeds.

In the process of this invention, the fibers are sprayed with water while on apron 18 until the mass of wetted fibers contains from about 0.3 to about 3.0 pounds of water for each pound of fiber. If less than 0.3 pound of water is used (per pound of fiber), the buoyant pneumacel fibers are not cohesively enough massed so as to prevent their being blown about by air currents within the machine. If more than about 3 pounds of water are used r pound of fiber) some water is thrown off by the ac on of stripper roll 30. Thus, the use of more than about 3 pounds of water (per pound of fiber) is unnecessary. Preferably, the sprayed fibers should contain between about 0.8 and about 2.0 pounds of water per pound of fiber. In this range the fibers are of good cohesiveness for batt formation and the heat load in subsequent drying steps is not excessive.

The water, which may contain up to about 0.1 percent by weight of water of a wetting agent, forms a film on the fibers, which lubricates the fibers and retards the build up of electrostatic changes.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described for obvious modifications will occur to those skilled in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In the process for separating gas-inflated, closedcell staple fibers from a source of supply of the fibers into individual fibers and depositing them in the form of a continuous batt, which comprises passing the fibers to an endless conveyor which forwards the fibers into engagement with an upwardly moving spiked lattice, removing the fibers fromsaid lattice and arranging them in the form of a batt, the improvement which comprises;

wetting the fibers prior to their engagement with the upwardly moving lattice until the wetted fibers contain between about 0.3 and about-3.0 pounds of water per pound of fiber, and

compressing the fibers into a mat as they are moved by the spiked lattice.

k k l 

1. In the process for separating gas-inflated, closed-cell staple fibers from a source of supply of the fibers into individual fibers and depositing them in the form of a continuous batt, which comprises passing the fibers to an endless conveyor which forwards the fibers into engagement with an upwardly moving spiked lattice, removing the fibers from said lattice and arranging them in the form of a batt, the improvement which comprises; wetting the fibers prior to their Engagement with the upwardly moving lattice until the wetted fibers contain between about 0.3 and about 3.0 pounds of water per pound of fiber, and compressing the fibers into a mat as they are moved by the spiked lattice. 